1. Field of the Invention
The present invention relates to the field of hair dryers, and in particular low noise, hand-held hair dryers.
2. Prior Art
Hand-held hair dryers are well-known in the prior art. Such devices are generally sold in various sizes and configurations, and with various features, though all are characterized by a body having a motor and fan for air movement, a heater for heating the air and a handle for the convenient holding and movement thereof. In general the body of such devices is metal or hard plastic, with the motor being directly supported by the body or handle so that the motor vibrations are directly transmitted thereto. In addition, the fan blades themselves create substantial noise, part of which is transmitted through the rigid housing of the dryer and part of which simply passes outward through the outlet and inlet regions of the hair dryer. Further, the air velocity in the region of the heater downstream of the fan is relatively high, though the structure in such region, such as the heater and heater supports, is usually perpendicular to the air stream with no consideration of streamlining thereof. The net result is that commercially available hand held hair dryers, while varying somewhat from design to design, all generate very substantial noise within the audible region, typically on the order of 70 db or higher at a distance of 18 inches therefrom. While the noise signatures of various units also vary, most tend to show substantial noise which is synchronous with the fan blade passing speed (motor speed.times.the number of fan blades) and harmonics thereof, with the remainder of the noise being substantially white and spread throughout the remainder of the audible range. While units recommended for professional use may be superior in terms of life and reliability, in general they are not superior with respect to the noise generated in comparison to consumer units.
The high noise level of prior art hand held hair dryers is undesirable for various reasons. In particular, the noise drowns out all other sounds, normally making it impossible to carry on a conversation with others, to listen to a radio or TV, to hear the doorbell or telephone ring, etc. Accordingly, it would be highly desirable to significantly reduce the noise generated by such hair dryers for both social and safety reasons; while maintainin high air flow and heat capacities. As shall be seen from the known prior art discussed below, no substantial progress had been made in this direction prior to the present invention. Grabner (U.S. Pat. No. 3,418,452) discloses a dryer for drying persons bodies with warm air after bathing. This dryer includes a sleeve of insulating material mounted inside the casing. The insulating material, however, is thermal insulation and not sound insulation for sound absorbing purposes. There is also included a strip of insulating material interposed between the motor and its mounting bracket to dampen vibrations. However, as the main body is also used as the propeller shroud, the energy transmitted by the blade tip to the housing will serve to negate the beneficial effect of the strip, resulting in noise and vibrations to the main body.
Ponczek et al. (U.S. Pat. No. 3,261,107) discloses a hair dryer which has "dampening" rings around the motor casing. However, the motor is rigidly coupled to the shroud by the use of metal vanes and a metal motor bracket. Also, the spacing between the shroud and outer shell halves is quite small. Thus not only will the vanes result in vortex shedding and increased upstream airborne noise, but the close undamped spacing of the shroud to the outer shell, in conjunction with the rigid coupling of the motor to the shroud, will allow vibrational energy to be directly transmitted to the outer shell.